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1 servomyces capsule is the correct dose for 5 galons of wort. If I want to add servomyces to my 1.5 litre yeast starter should i break open the capsule and use only part of it? or is it safe to add the whole capsule?

Is there any risk of osmotic pressure on the yeast if using the whole capsule in the starter? Can you suggest a better product or method for adding nutrient to a starter?

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I can't attest to the actual #s, but the zinc and other micronutrients are at trace levels in comparison to the macronutrients in the wort. My instinct as a cell biologist is that even at 5X-10X the concentration (1 capsule in a starter) isn't enough to change the osmolarity of the solution significantly. I'd post it as an answer, but I simply don't know the actual #s so I am just postulating... but that's a very educated guess. –  brewchez Sep 26 '12 at 22:34

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Servomyces is simply dead yeast. Prior to being killed, it was fed micronutrients which have been stored in the yeast. There's no harm pitching more into your starter, assuming you then later pitch to 5 gallons or more. If your starter yeast don't use all the nutrients, your main brew certainly will, so there's no harm pitching the entire capsule.

The White Labs FAQ says this about Servomyces

Servo is yeast and is propagated in a micronutrient rich environment then, and is killed off prior to packaging. Boiling incorporates the Servo into the wort. The benefit of Servo is that micronutrients, e.g. zinc, are able to pass through its cell walls to your live yeast cell, thereby delivering the micronutrients without toxicity. Because this system is so effective in eliminating autolysis and improving the health of your yeast, it should be used in every batch.

As to alternatives, I use Wyeast's nutrient blend and put 1/2 tsp, recommended for 5 gallons, in a 2 liter starter. The cell counts have been good. I see no reason why this wouldn't also hold for white lab's nutrient. I think the main concern is flavor thresholds, not toxicity, or osmotic pressure required by the cell to maintain equilibrium.

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The only down side to this approach is the cost. The FAQ is useful but it doesn't say specifically about dosages. How do we know the zinc or something else at these concentrated levels is not going to be harmful? –  mR_fr0g Sep 25 '12 at 16:02
    
My reasoning is that it's the same quantity of live yeast if you pitch a vial into a starter or into a 5 gallon batch. The amount of nutrients per cell is the same. If cost is a problem, then use the wyeast nutrient blend - it costs a fraction of servomyces per brew. –  mdma Sep 25 '12 at 21:43
    
Its not the yeast to zinc ratio that is in question. Its the zinc to water ratio that may or may not create an osmotically unfavorable starter wort. (I don't think it does. The zinc is likely present at levels below even the NaCl levels for the wort itself, but I have no evidence because even White labs doesn't exactly quantify this #. I just can't imagine there is that much zinc present to change the osmolarity of the wort.) –  brewchez Sep 26 '12 at 22:26
    
I use wyeast's nutrient blend and put 1/2 tsp, recommended for 5 gallons, in a 2 liter starter. The cell counts have been good. I see no reason why this wouldn't also hold for white lab's nutrient. I think the main concern is flavor thresholds, not toxicity, or osmotic pressure required by the cell to maintain equilibrium. The quantities of micronutrients are simply too low. –  mdma Sep 27 '12 at 8:55

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